The present invention relates to prostheses and more particularly to volume compensation devices for adjusting the fit of a prosthetic socket to a residual limb.
Those individuals who have suffered an amputated limb are generally fitted with prosthetic devices which are provided with a socket into which the residual limb is inserted. Maximum usefulness of artificial limbs is enhanced by maintaining a close and comfortably fitting prosthetic socket.
One critical problem in assuring such a close and comfortable fit for a prosthetic socket is that the fit of the prosthetic socket is affected by daily variations in the volume of the residual limb. For example, merely walking on a residual limb may cause the volume of the limb to be reduced to the point that a comfortably fitting socket becomes unacceptably loose fitting.
In the past various inflatable or volume adjustable devices have been proposed for use in conjunction with prosthetic sockets. These devices, however, have primarily been directed toward the functions of cushioning the end of the residual limb or of a clamping action to assure the securing of a prosthetic appliance to a residual limb.
For example, U.S. Pat. No. 4,842,608 issued to Marx et al. on Jul. 27, 1989 for "Fluctuating Volume Adjustable Preparatory Below Knee Prosthetic Socket", a pair of cooperating rigid plastic supports relatively adjustable to accommodate volume changes in residual limbs. However, Marx is primarily directed to the problem of post-operative changes in residual limb volume and not to daily variations.
Numerous air or fluid inflatable prosthetic devices have been developed essentially to act as a substitute for a custom fitted prosthetic socket. These devices are designed to cushion the residual limb and to provide a tight fit for securing the residual limb to the prosthetic device. For example, U.S. Pat. No. 2,634,424 issued to O'Gorman on Apr. 14, 1953 for "Artificial Leg" discloses a prosthetic socket made of a resiliently flexible material whose walls are spaced apart to provide an air-tight cavity with a series of webs dividing it into a number of interconnected departments. The device completely encircles the residual limb and is provided with mean to inflate or deflate the device. The device, however, is not designed to readily accommodate short term daily fluctuations in the volume of the residual limb. Likewise, U.S. Pat. No. 3,393,407 issued to Kandel on Jul. 23, 1968 for "Artificial Limb with End-Bearing Socket and Method of Making" is also primarily a substitute for a custom fitted socket. No means to adjust the volume of the socket is provided. U.S. Pat. No. 3,889,30 issued to Bonner on Jun. 17, 1975 for "Therapeutic Stump Treating Air Sac Prosthesis" falls in the same category. U.S. Pat. No. 4,655,779 issued to Janowiak on Apr. 7, 1987 for "Air System Prosthesis for Amputees" provides for a manual means to inflate and deflate an air sac which completely surrounds the residual limb. While Janowiak provides means for adjusting the volume of the prosthetic socket, Janowiak, likewise, is directed to a device which substitutes for a custom-made socket and includes features primarily designed to cushion the residual limb and to assist in securing the prosthesis to the residual limb.
In the same category of inflatable devices whose primary purpose is to provide cushioning for the end of the residual limb is U.S. Pat. No. 4,923,475 issued to Gosthnian, et al. on May 8, 1990 for "Inflatable Limb Prosthesis with Preformed Inner Surface." Gosthnian discloses a prosthesis having a socket with a plurality of inflatable bladders. The inflatable bladders are located in such a way as to cushion the weight bearing portions of the residual limb. A variant cushioning device is disclosed in U.S. Pat. No. 4,432,101 issued to Johnson on Feb. 21, 1984 for a "Cushioning Patellar Support Device." Johnson discloses a butterfly shaped inflatable/deflatable bag for cushioning the weight bearing portions of the residual limb in conjunction with a below-the-knee prosthesis.
An example of an inflatable device designed primarily to secure the residual limb to the prosthesis is disclosed in U.S. Pat. No. 3, 671,980 issued to Baird on Jun. 27, 1972 for "Fluid Pressure Clamp for Prosthetic Appliance." Baird discloses a fluid pressure wedge for securing a prosthetic appliance to the residual limb.
None of the cited devices, however, is uniquely adapted to the problem of daily fluctuations in the volume of a residual limb when used in conjunction with a normal, custom-fitted prosthetic socket.